Interleukin-8-induced transcellular neutrophil migration is facilitated by endothelial and pulmonary epithelial cells

Interleukin-8 (IL-8) is an 8,000 D protein produced by many cells and has potent neutrophil chemoattractant and activating properties. Indeed, there is substantial data supporting a role for IL-8 in neutrophilic lung inflammatory responses. In vivo, neutrophils must adhere to and then migrate across endothelial and epithelial cell barriers in order to reach inflammatory foci. Therefore, we examined IL-8-induced neutrophil migration through naked filters and through human umbilical vein endothelial (HUVE) cells and human pulmonary type II-like epithelial cells (A549) cultured on these filters. IL-8 induced both dose- and time-dependent migration of neutrophils across all three barriers. At IL-8 concentrations greater than 10(-8) M, neutrophil migration across both endothelial and epithelial cell barriers was significantly greater than that observed across naked filters. In addition, time-course experiments indicated that neutrophil migration continued to occur for up to 3 h across both cellular barriers while neutrophil migration across naked filters plateaued by approximately 60 to 90 min. Migration of neutrophils through all barriers was completely inhibited by anti-IL-8 neutralizing antibody. The increased migration observed through both cellular barriers was not due to either changes in chemotactic gradients or the production of other soluble chemotactic factors by IL-8-stimulated HUVE and A549 cells versus naked filters. Furthermore, pretreatment of monolayers with actinomycin-D had no effect on the degree of transcellular migration. Thus, the facilitation of neutrophil migration through HUVE and A549 monolayers is not dependent upon new protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)